Comparison of different space time coding for transmit diversity in VLC systems with CSK modulation

This paper investigates the transmit diversity techniques in visible light communication system with color shift keying modulation using RGB LEDs. The Alamouti-type space time coding scheme suitable for CSK signals in VLC systems is proposed, which is a modification of Alamouti coding scheme in RF wireless systems. The signal constellations of CSK signals are redesigned to be applied in the Alamouti-type coding scheme. Besides, The repetition coding is presented as well. Performance comparison has been made between the Alamouti-type coding scheme and the repetition coding scheme. It is find out that both coding schemes are able to extract full diversity order. Simulation results demonstrate that repetition coding performs almost the same as Alamouti-type coding when the same constellations are employed. Our findings clearly point out that the deployment of Alamouti-type coding is not necessary in VLC systems with CSK modulation and the reason for this conclusion is discussed at last.